The Labour Party and teacher unions are panning a National-Act proposal for charter schools as a step towards privatising the education system with a proposal that neither party put forward before the election.
Charter schools - effectively state-funded private schools - will be introduced to South Auckland and Christchurch within the next three years as part of the confidence and supply deal between the National and Act parties.
The goal of charter schools is to lift the performance of low-achieving students by giving schools more flexibility and autonomy - including the possibility of for-profit private management, an independent curriculum and performance-pay for teachers, which teach unions are vehemently opposed to.
Charter schools will be expected to be faith-based with an academic focus on approved curriculum and qualifications. They can raise revenue through partnerships or sponsorship with iwi, community groups or the private sector.
Prime Minister John Key said the proposal was in its early days and he did not know how a school would qualify to be a charter school, or how many schools or students will be affected.
The schools could become a permanent part of the education landscape.
"We're going to trial that ... but over time you can see a new category of schooling," Mr Key said.
But NZEI president Ian Leckie said the Government had no mandate for charter schools.
"Overseas experience shows they can take students and money away from existing schools, undermine communities and increase social segregation. They are also less accountable.
"New Zealanders should be very concerned that Act is suddenly shaping and dictating key education policy."
Labour's education spokeswoman Sue Moroney called the trial "bulk-funding in drag" and exposed National's true colours.
But Mr Key said the idea came from Act.
Act did not have an election policy of charter schools, but did promote greater autonomy and performance-pay for teachers.
Charter schools overseas have had mixed results, with some improved learning outcomes amid accusations they have been used as a vehicle for religious indoctrination.
Strict accountability has been singled out as a key component of success. The National-Act agreement says schools will be accountable to their sponsors and subject to external review, perhaps by the Education Review Office.
School sponsors will be responsible for setting goals and operational standards.
The New Zealand model will be based on the Knowledge is Power Programme in the US - which involves about 100 schools and 27,000 students from primary to high school- and to some extent the UK system.
KIPP has been lauded for improvements in maths and reading, but criticised for selecting the most motivated students; the National-Act proposal is for charter schools to have to accept all student applicants, regardless of academic ability.
A recent study found that 33 per cent of students who completed a KIPP at least 10 years ago have a university degree today, compared to 8 per cent of similar students nationwide.
NZ Principals' Federation president Peter Simpson said the trial was a significant step and the sector had to be involved in the consultation process.
An implementation group including representatives from the private sector, business, iwi and community groups will be set up, with its terms of reference to be drawn up by National and Act, with help from the Education Ministry.